1. Field of the Invention
The field of the invention relates to air purifiers, particularly to portable air purifiers including HEPA filters.
2. Brief Description of the Prior Art
Portable air purifiers for removing airborne particles are used in many homes and offices. Such purifiers often include a fine particle high efficiency particulate air (HEPA) filter. In addition to a HEPA filter, some purifiers include a carbon filter to remove odors. The carbon may be incorporated within a fibrous matrix. A filter for trapping relatively large particles may also be found in portable air purifiers. In operation, one or more fans cause air to be drawn through the filter(s) and emitted through an outlet.
HEPA filters have gained increasing acceptance for use in purifiers directed to consumers as they remove 99.97% of particles having a size equal to or greater than 0.3 microns. In order to take full advantage of a HEPA filter or any other type of filter used in an air purifier, it is important to ensure that substantially all of the air emitted by the air purifier has indeed first passed through the filter(s) provided in the purifier. Where a filter includes both a HEPA component and filter component, the lifespan of the filter is generally dependent upon the carbon component. This is because the trapping capacity of the carbon component is generally exhausted prior to that of the HEPA component.
As the filter(s) employed in air purifiers require replacement when spent, the ability to easily remove and replace the filter(s) is important. A replaced filter must be properly installed if it is to function properly. Disposable filter assemblies have accordingly been designed to facilitate user convenience.
Currently portable air purifiers are manufactured in various sizes with different capacities to suit a consumer""s particular needs. The larger capacity air purifiers generally require larger sized filters. This generally requires retailers to stock a plurality of different size filter elements to satisfy the demands of all consumers. Replacement HEPA filter elements are traditionally bulky and expensive inventory for retailers to maintain. The retailer must stock the replacement filters for every air purifier that is sold, but the filters generally do not need replacement very frequently. The retailers that carry air purifiers are required out of necessity to offer a line of different size units that are expensive to purchase, do not turn over very often, and take up a lot of shelf space. In addition, to exacerbate the problem it has been found that by the time the consumer needs to replace the filter element, the inventory is old and looks beat up.
A general problem associated with air purifiers is that the devices create noise which can be disturbing to the user. Most of the noise attributed to the air purifier is attributed to the airflow through the unit. Generally the noise levels generated by the unit will increase with the volume of airflow passing through the unit. In addition, the overall size of the unit is important too because it is also known that if portable purifiers could be made larger (while remaining portable) the unit would be quieter. Accordingly when assessing the performance characteristics of an air purifier the volume or Clean Air Delivery Rate (xe2x80x9cCADRxe2x80x9d), size and noise generated must all be considered.
A number of patents have issued which disclose air purifiers including HEPA filters, carbon filters, and/or other filters. U.S. Pat. Nos. 3,928,008; 4,378,983; 4,521,234; 4,629,482; 4,737,173; 4,778,496; 5,078,764; 5,102,435; 5,131,932; 5,230,723; 5,259,854; 5,290,330; 5,512,086; and 5,893,939 disclose air purifiers of various constructions. The disclosure of the U.S. Pat. No. 5,893,939 is incorporated herein by reference.
A portable air purifying device is provided for removing airborne particles. The device includes a housing including an exterior surface formed with an air inlet and an air outlet. The air outlet is formed as a plurality of openings. A scroll is located within the housing and has walls formed with an intake opening and an exhaust port. The exterior surface and the walls define a cavity. The cavity has a first portion and a second portion. The first portion is in communication between the exhaust port and the air outlet. A fan is positioned within the intake opening for drawing air in through the air inlet to pass through the scroll and the first portion of the cavity to be expelled through the air outlet while the second portion of the cavity is under a positive pressure. A filter assembly is positioned within the housing between the air inlet and the fan.
In a first preferred embodiment, the plurality of openings of the air outlet are formed as a grill. The scroll preferably includes an exhaust duct portion having a first end and a second end with the walls defining a cross section of the exhaust duct portion. The first end is in fluid communication with the intake opening and the second end terminates at the exhaust port. Preferably the cross section increases between the first end and the second end. Preferably the walls of the scroll are configured to form a reducer at the intake opening having a cross section. The fan preferably includes a motor mount assembly connected to one of the housing or the scroll, and a fan blade coupled to the motor mount assembly and positioned within the scroll adjacent to the reducer. Preferably the cross section of the reducer is circular and decreases from the intake opening towards the fan blade. The motor mount assembly preferably includes a motor) a motor mount ring, and a plurality of brackets. The motor preferably has a shaft for coupling to the fan blade. The motor mount ring is preferably attached to the motor and has a center. Each of the brackets preferably has a pronged end attached to the motor mount ring and extending radially from the center, and a curved end for connecting to one of the housing or the scroll. Preferably a wire ring is connected to at least two of the plurality of brackets adjacent to the curved end. Preferably a grommet is located at the curved end of each bracket.
In an alternative embodiment, a portable air purifying device includes a housing, a fan, and at least two filter assemblies. The housing includes an air inlet and an air outlet. The fan is positioned within the housing for drawing air into the housing through the air inlet and expelling air through the air outlet. The modular filter assemblies are positioned within the housing in parallel between the air inlet and the fan. Each of the filter assemblies include a frame and a filter element mounted to the frame. Preferably the housing includes a door configured to engage the filter assemblies. Preferably each of the filter assemblies has a second filter element in series with the filter element. Most preferably the filter element is a HEPA filter and the second filter element is a removably attached carbon filter.
A family of portable air purifying devices is also presented in accordance with the present invention. The family includes a plurality of portable air purifying devices. Each of the plurality of portable air purifying devices include a housing, a fan, and a number of modular filter assemblies. The housing includes an air inlet and an air outlet. The fan is positioned within the housing for drawing air into the housing through the air inlet and expelling air through the air outlet. The number of modular filter assemblies are positioned within the housing in parallel between the air inlet and the fan. The filter assemblies have a frame and a filter element mounted to the frame. The number for at least one of the plurality of portable air purifying devices is different from the number for another of the plurality of portable air purifying devices.